ACPA Quarter 2 2016

Concrete Pavement Progress

www.acpa.org

and cementitious products, explained Steve R.

Schmidt, vice president and concrete paving

division manager at Northern Improvement

Company, the project’s paving contractor. “The

locally available aggregates are reactive and there-

fore we had to mitigate ASR. Substituting fly ash

for Portland cement reduced the ASR but was not

sufficient tomeet the FAA specifications,” he said.

FAA standard specifications also utilize flexural

strength for acceptance, pointed out Schmidt.

“Although the locally available aggregates are

excellent in compression, they would not meet

the specifications for flexural strength regardless

of the amount of cementitious material used.”

Ten mix designs were completed before a mix

design meeting both the ASR specification and

the flexural strength specification was found.

“We tried various water reducers, various dos-

age rates, and increased cementitious material

but none of these solutions would produce a

mix meeting the flexural specifications,” said

Schmidt. “We changed aggregate sources and

the strengths improved but not enough to meet

the specification.”

After meeting with the technical experts from

Terracon, which completed the mixes and trials;

Braun Intertec, which completed the quality

control testing; Lafarge, the cement and fly-

ash supplier; and GCP Applied Technologies

(formerly Grace Construction Products), the

admixture supplier, a change to the water reducer

along with new aggregates finally produced a

mix meeting the FAA’s specifications. “The new

aggregates, which we imported fromWyoming,

were also non-reactive, which eliminated the

need to mitigate with special ad-

mixtures,” pointed out Schmidt.

For the volume and type of aircraft

using the Bowman airport, a 6-inch

concrete pavement was more than enough

but that thickness proved to be a challenge, said

Brennan.

There were a lot of factors that contributed to the

success of the project, including the ability to

work over several construction seasons, a team

that worked together to solve problems, and the

use of alternate bids and LCCA to take advantage

of concrete’s price advantage at the time.

“The concrete pavement will not only extend the

service life of the airport by supporting greater

volume and weight, but it will also reduce main-

tenance costs,” said Brennan. “As the lieutenant

governor said at the grand opening: Selection of

concrete for this project means that the Bowman

Airport will allow aircraft three times heavier

and last three times longer compared to other

pavement products.”



Tech Tour Tackles Airport Pavement Issues

A three-day whirlwind tour of North Dakota by Gary Mitchell, vice president of Airports & Pavement

Technology for the American Concrete Pavement Association (ACPA), and Dave Sethre, executive

director of the North Dakota Chapter—ACPA, gave airport pavement designers and owners’ rep-

resentatives an opportunity to learn more about FAA airport pavement specifications—particularly

those related to processes and local materials that have caused issues in the state.

Mitchell said they also spoke with officials at North Dakota Aeronautics Commission and FAA’s

district office officials with the goal of modifying specifications. He added the FAA officials pledged

to advance the information through channels with the expectation of modifying specifications that

have been problematic for contractors, consultants and owner’s representatives.



Bowman Regional Airport

received the Gold Award in the

Reliever & General Aviation Airports

category of the American Concrete

Pavement Association’s 26th Annual

“Excellence in Concrete Pavement”

awards in December 2015.

b o w m a n a i r p o r t

» Aviation Project, cont.